Search Publications
Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyond
Fabian, A. C.; Sanders, J. S.; Walker, S. A.
The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high-energy astrophysics. Here we explore applications of Gaussian gradient magnitude (GGM) filtering to X-ray data, which dramatically improves the clarity of surface brightness edges in X-ray observations, and maps gradients in X-ray s…
Ion chemistry in the coma of comet 67P near perihelion
Gunell, H.; Wurz, P.; Altwegg, K. +33 more
The coma and the comet-solar wind interaction of comet 67P/Churyumov-Gerasimenko changed dramatically from the initial Rosetta spacecraft encounter in 2014 August through perihelion in 2015 August. Just before equinox (at 1.6 au from the Sun), the solar wind signal disappeared and two regions of different cometary ion characteristics were observed…
A porosity gradient in 67P/C-G nucleus suggested from CONSERT and SESAME-PP results: an interpretation based on new laboratory permittivity measurements of porous icy analogues
Thomas, N.; Brouet, Y.; Pommerol, A. +12 more
The Rosetta spacecraft made a rendezvous with comet 67P/Churyumov-Gerasimenko (67P) in 2014 August, soon after the Philae module landed on the small lobe of the nucleus on 2014 November 12. The CONSERT instrument, onboard Rosetta and Philae, sounded the upper part of the interior of 67P with radiowaves at 90 MHz and determined an average of the re…
NLTE carbon abundance determination in selected A- and B-type stars and the interpretation of C I emission lines
Mashonkina, L. I.; Alexeeva, S. A.; Ryabchikova, T. A.
We constructed a comprehensive model atom for C I-C II using the most up-to-date atomic data available and evaluated the non-local thermodynamic equilibrium (NLTE) line formation for C I and C II in classical 1D models representing the atmospheres of A- and late B-type stars. Our NLTE calculations predict the emission that appears at effective tem…
A recent change in the optical and γ-ray polarization of the Crab nebula and pulsar
Hallinan, G.; Laurent, P.; Moran, P. +4 more
We report on observations of the polarization of optical and γ-ray photons from the Crab nebula and pulsar system using the Galway Astronomical Stokes Polarimeter (GASP), the Hubble Space Telescope, Advanced Camera for Surveys and the International Gamma-Ray Astrophysics Laboratory satellite (INTEGRAL). These, when combined with other optical pola…
A low-luminosity soft state in the short-period black hole X-ray binary Swift J1753.5-0127
Altamirano, D.; Charles, P. A.; Gandhi, P. +6 more
We present results from the spectral fitting of the candidate black hole X-ray binary Swift J1753.5-0127 in an accretion state previously unseen in this source. We fit the 0.7-78 keV spectrum with a number of models, however the preferred model is one of a multitemperature disc with an inner disc temperature kTin = 0.252 ± 0.003 keV sca…
Modelling the evolution of a comet subsurface: implications for 67P/Churyumov-Gerasimenko
Guilbert-Lepoutre, Aurélie; Rosenberg, Eric D.; Prialnik, Dina +1 more
Modelling the evolution of comets is a complex task aiming at providing constraints on physical processes and internal properties that are inaccessible to observations, although they could potentially bring key elements to our understanding of the origins of these primitive objects. This field has made a tremendous step forward in the post-Giotto …
Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta
Jorda, L.; Lamy, P. L.; Lara, L. M. +58 more
Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study th…
The Gaia spectrophotometric standard stars survey - III. Short-term variability monitoring
Jordi, C.; Figueras, F.; Marinoni, S. +14 more
We present the results of the short-term constancy monitoring of candidate Gaia Spectrophotometric Standard Stars (SPSS). We obtained time series of typically 1.24 h - with sampling periods from 1-3 min to a few hours, depending on the case - to monitor the constancy of our candidate SPSS down to 10 mmag, as required for the calibration of Gaia ph…
The Chandra ACIS Timing Survey Project: glimpsing a sample of faint X-ray pulsators
Sidoli, L.; Esposito, P.; Israel, G. L. +1 more
We report on the discovery of 41 new pulsating sources in the data of the Chandra Advanced CCD Imaging Spectrometer, which is sensitive to X-ray photons in the 0.3-10 keV band. The archival data of the first 15 yr of Chandra observations were retrieved and analysed by means of fast Fourier transforms, employing a peak-detection algorithm able to s…